1. Field of the Invention
This invention relates generally to a side crane, and more particularly to a device for elevating the boom of a side crane which is adapted for naturally lowering and hydraulically forcibly lifting or lowering the boom so as to maintain the boom without the necessity of continued oil supply from a pump in a forcibly lowering or lifting state for a long time.
2. Description of the Prior Art
In conventional side cranes, there are generally two types of devices for lifting and lowering the booms thereof, namely the cable type and the hydraulic type, and the lowering of a side crane of the cable type is obtained under the force of its own weight, and that of the hydraulic type is obtained generally in the same manner as that of cable types, but they do not provide for such lowering forcibly. Therefore, the conventional side crane cannot serve in a pushing operation by utilizing the boom, nor can the vehicle body be prevented from falling down by forcible operation of the boom.